Method of aligning a two-capillary tube gas discharge device

ABSTRACT

A metal rod is inserted through the left and right capillary tubes of a gas discharge device. One end of a coaxial bulb joining one capillary tube is heated until the glass thereof is softened. Then, the metal rod is rotated within the two capillary tubes until the bores thereof are axially aligned. Then, the softened end of the bulb is allowed to cool to fix the aligned capillary tubes. Then, the metal rod is removed from the discharge device.

' July 16, 1974 w. E. RlGGL-E v 3,824,089

METHOD OF ALIGNING A TWO-CAPILLARY TUBE GAS DISCHARGE DEVICE Filed Aug. 20, 1973 METHOD OF ALIGNING A TWO-CAPILLARY TUBE GAS DISCHARGE DEVICE William Eugene Riggle, Lancaster, Pa., assignor to RCA Corporation, New York, N.Y. Filed Aug. 20, 1973, Ser. No. 389,719 Int. Cl. C03b 23/08 US. Cl. 65-109 4 Claims ABSTRACT OF THE DISCLOSURE A metal rod is inserted through the left and right capillary tubes of a gas discharge device. One end of a coaxial bulb joining one capillary tube is heated until the glass thereof is softened. Then, the metal rod is rotated Within the two capillary tubes until the bores thereof are axially aligned. Then, the softened end of the bulb is al lowed to cool to fix the aligned capillary tubes. Then, the metal rod is removed from the discharge device.

. BACKGROUND OF THE INVENTION This invention relates to a method of axially aligning two capillary tube bores for a gas discharge device, and particularly, but not exclusively, to an interferometer gas discharge device.

An interferometer gas discharge device may use two separate capillary tubes, each of which is supported in a cantilevered suspension by one of two respective ends of a coaxial bulb. Since the capillary tubes provide the output discharge from the tube, it is desirable to align the bores as accurately as possible.

In one prior method of alignment, a straight metal rod is inserted through the bores of both of the capillary tubes, and then the capillary tubes are fused to ends of a coaxial bulb. Although this method should provide an accurate alignment, in practice the metal rod does not adequately support both capillary tubes; therefore the desired alignment is not achieved. An inaccuracy in bore alignment may result in the nonoperation or in an unsatisfactory operation of the gas discharge device. If an improperly aligned gas discharge device does operate, the output discharge will be sacrificed, or the device may operate at a multiple discharge frequency instead of the desired single frequency, making it unsatisfactory for its intended use.

SUMMARY OF THE INVENTION In the manufacture of a gas discharge device, including two separate capillary tubes having central bores therethrough, each tube being supported in a cantilevered suspension by one of two respective ends of a coaxial bulb, the two capillary tubes are aligned by inserting a metal rod through the bores of both capillary tubes. Then, one end of the bulb is heated until the glass thereof is softened. Then while the gas discharge device is maintained stationary, the metal rod is rotated Within the capillary tubes until the bores thereof are aligned. Then, the softened connecting bulb end is allowed to cool to fix the bores in axial alignment. Then the metal rod is removed from the gas discharge device.

BRIEF DESCRIPTION OF THE DRAWINGS The sole Figure is a sectional view of a portion of a gas discharge device illustrating one step in the novel method.

DESCRIPTION OF THE PREFERRED EMBODIMENT The Figure of the drawing illustrates an assembled interferometer type gas discharge device 10. The gas discharge device 10 includes a left capillary tube 11 and a United States Patent ice right capillary tube 12 supported cantilevered within a coaxial bulb 13. The bulb 13 is connected to the left capillary tube 11 with a left end section 14 and to the right capillary tube 12 with a right end section 15, both of which are fused to the outside walls of the left and right capillary tubes 11 and 12.

A cylindrical cold-cathode 16 is positioned within the bulb 13 with its outer surface substantially coinciding with the inner surface of the bulb 13. The cathode 16 is connected to at least one conductive pin 17 which extends through the bulb 13 by a metal conductor 18.

The left capillary tube 11 has a central bore 19 of about 0.0400-inch diameter therethrough. A first anode region 20 communicating with the bore 19 is positioned in a relatively long portion 21 of the left capillary tube 11 which extends from the left end of the bulb 13. The first anode region 20 is formed by a closed hole in the wall of the first capillary tube 11. A first anode pin 22 connects the first anode region 20 through the wall of the left capillary tube 11 to the outside of the device 10. The right capillary tube 12 similarly includes a central bore 23 of about 0.0400-inch diameter therethrough, a second anode region 24 communicating with the bore 23, and a second anode pin 25 connecting the second anode region 24 to the outside of the device 10.

The left end 26 of the left capillary tube 11 includes a first light output window 27, and the right end 28 of the right capillary tube 12 includes a similar second light output window 29. Although light output windows are described, where a lasing output discharge is desired, reflecting members such as mirrors may also be used.

In operation, the gas (preferably He-Ne) through which the electrical discharge occurs is confined within the bulb 13 at a very low pressure. To establish the electrical discharge, a suitable power supply of conventional design (not shown) is connected between both the first and second anode pins 22 and 25 and the cathode pin 17, as is known. During the operation of the tube 10, electrons emitted from the inner surface of the cathode 16 travel into the open end 30 of the left capillary tube 11 and through the central bore 19 thereof to the first anode region 20 where they are collected. Similarly, the electrons from the cathode 16 travel into the open end 31 of the right capillary tube 12 and through the central bore 22 thereof to a second anode region 24. The emitted electrons interact with the gas within the device 10 thereby ionizing a portion of the atoms thereof and creating the desired discharge.

To obtain the most optimum discharge, the axial alignment of both the central bores 19 and 23 must be concentric at both the open ends 30 and 31 and straight within a tolerance of 0.003 total indicated runout. The novel alignment method which will be described accomplishes this requirement.

In the novel method, the left and right capillary tubes 11 and 12 are aligned by positioning a partially assembled device 10 (less first and second light output windows 27 and 29) on a metal rod 32 about 0.0395 inch in diameter and about 2 /2 times the overall length of the assembled device 10. It is preferred that the metal rod is tungsten although stainless steel may be used. The rod 32 with the partially assembled device 10 thereon is then clamped between a headstock chuck 33 and a tailstock chuck 34 of a glass sealing lathe (not shown). Then the tailstock chuck 34 is adjusted until there is approximately pounds per square inch tension on the rod 32 and then locked to maintain this tension.

The device 10 is then moved adjacent the headstock chuck 33, and a length of the rod substantially equal to the length of the right capillary tube 12 is heated to a temperature of about 200 C. The device 10 is then moved over the heated length of the rod 32, and the right end section 14 in the area where it is fused to the right capillary tube 12 is heated until the glass comprising the right end section 14, at least adjacent the right capillary tube 12, is softened and workable. As soon as the glass is workable, the rod 32 is rotated at about 50 r.p.m. within both central bores 19 and 23. During the rotation the device is held stationary. It is preferred that the device 10 be held by the relatively cool left capillary tube 11 to prevent any undesirable distortion of the bulb 23 which may occur near the softened right end section 15. The rotation of the rod 32 causes the adjacent open ends 30 and 31 of both capillary tubes 11 and 12 to move into a concentric orientation and causes the entire right capillary tube to translate within the softened portion of the right end section 15 until the central bore 23 in the right capillary tube 12 is in the above described desired axial alignment with the central bore 19 in the left capillary tube 11.

Although it is described that the alignment is achieved by softening the right end section, it must be realized that the tube is symmetrical; therefore this alignment could also be performed by softening the left end section. Also, for badly aligned capillary tubes, sequential alignment may be accomplished by first using the novel method on one end section and then on the other end section. Although it may be possible to simultaneously heat both end sections 14 and 15 and achieve the desired result, it is preferred that the alignment be accomplished sequentially to avoid distortion of the device 10.

The right end section 15, the bulb 13, and the right capillary tube 12 are then flame annealed, as is known, to remove the possible stresses. Then the connecting end portion is allowed to cool to fix the bores in axial alignment. The device 10 is then removed from the rod 32, and the windows 27 and 29 are attached, as is known. The novel method provides accurate alignment of the bores of the two capillary tubes, resulting in an increased efficiency of the gas discharge device.

I claim:

1. In the manufacture of a gas discharge device comprising two separate capillary tubes each having a central bore therethrough, each tube being supported in a cantilevered suspension by one of two respective ends of a coaxial bulb, the method of axially aligning the bores of said capillary tubes comprising the steps of (a) inserting a metal rod through both bores,- I

(b) heating one bulb end portion until said glass is softened, 1

(c) then, while maintainingsaid device stationary, ro-

tating said metal rod within said bores whereby said,

bores are axially aligned, ((1) then allowing said connecting end portion to fix said bores in said axial-alignment, (e) and, then removing said metal rod from said device. 2. The method defined in claim -1 comprising the adto cool ditional step between steps (a) and (b) of tensioning said metal rod. 4

3. The method defined in claim 2 wherein said tensioning said metal rod comprises mechanically tensioning said rod with about pounds per square inch of axial load.

4. The method defined in claim 3 wherein the outside diameter of said metal rod is about 0.005 inch less than the internal diameter of said bores of said capillary tubes.

References Cited UNITED STATES PATENTS 

